Now officially a teenager, Google has celebrated turning 13 in its customarily simple manner with a doodle showing the six letters of the company logo sitting around a cake.

With the search engine giant barely out of short trousers, the birthday celebrations come at a time when it is locked in an increasingly intense rivalry with an even younger pretender, Facebook.

Amid suggestions that Facebook could become the default form of online navigation, Google recently tried to overhaul its rival with Google+.

Research from Nielsen earlier this month showed that US internet users spend more time on Facebook than any other website.

At the same time, Google enjoys a 90% share of the global internet search market, according to the most recent figures from metrics firm StatsCounter, although its share varies considerably by country.

The doodle is in keeping with Google's low-key approach to celebrating its birthday. Unlike other doodles, it has no animated features and is based instead on a simple design.